Copolymers from α-β-unsaturated dicarboxylic acid esters, and their use

ABSTRACT

Lubricant or lubricant additives comprising copolymers of α-β-unsaturated dicarboxylic acid esters and α-olefins. When the olefin to ester ratio is 0.5 to 4.0 the α-olefins may have 10-16 C-atoms and the α-β-unsaturated dicarboxylic acid is esterified with straight-chain and/or branched monoalcohol of 3-10 carbon atoms. When the ratio is less than 2.0 the α-olefin is C 16  and the esterifying component may be C 4  -C 10  alcohol. The copolymers are useful as synthetic lubricating oils, mineral oil additives, lubricant additives and as lubricants for the shaping treatment of thermoplastic plastics.

This application is a continuation-in-part of U.S. Ser. No. 07/945,837 filed Oct. 21, 1992, abandoned which is a continuation of U.S. Ser. No. 07/000,893 filed Jan. 6, 1987, now abandoned, which is a continuation of U.S. Ser. No. 06/418,402 filed Sep. 15, 1982, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention concerns copolymers of α-β-unsaturated dicarboxylic acid esters with α-olefins, their production and their use.

2. Description of the Prior Art

Olefin-maleic acid-copolymer derivatives are known from German Offenlegungsschrift DE-OS 2,727,329, which are constructed from olefins with an average of 2-24 carbon atoms and maleic acid and are converted into esters with monovalent alcohols having a chain length from 2-20 carbon atoms in a mole ratio 1:0.5 to 1:2 maleic acid to alcohol. The there described olefin-maleic acid-copolymer derivatives are produced through copolymerization of maleic acid anhydride with α-olefins and subsequent esterification into semi- or diesters. The there described olefin-maleic acid-copolymer derivatives are particularly suitable for the lubricants in the shaping treatment of synthetics, i.e. plastics. These products are semi-solid to solid at room temperature. Their pour point always lies clearly above 0° C.

In other respects, high-molecular copolymers from α-olefins and from α-β-unsaturated dicarboxylic acid esters have been known, for example as hair sprays (AU-PS 254,327) and as agents for the coating of medicines (AU-PS 263,011). These were produced through copolymerization of α-olefins and α-β-unsaturated dicarboxylic acids or acid anhydrides and supplementary esterification of the copolymers, and are wax-like to solid at room temperature.

A copolymer of a C₂₂ -C₂₈ -1-olefin and dibehenylmaleate is known from German Offenlegungsschrift DE-OS 1,770,860, and is obtained by polymerization at 150° C. It is described as a wax-like product. It was suggested to mix hydrocarbons with the product, in order to lower the pour point or altogether to improve the flowability.

In DE-OS 1,770,860 it is set forth that the flowability improvement can only be obtained with such ester-polymers in which the number of carbon atoms in the alkyl part of the ester amounts to more than 20.

Flowability improvers for wax-like hydrocarbon oils are described in AU-PS 479,746, which effect a lowering of the pour point of the hydrocarbon-oil. Here also, expressly long side chains for the alcohol component of the dicarboxylic acid esters have been described as unconditionally necessary. The consistency of the product at room temperature is wax-like to solid. The pour point thus here also lies clearly above 0° C.

U.S. Pat. No. 2,615,845 to Lippincott et al. describes a copolymer of an unsaturated dicarboxylic anhydride and various olefins of chain lengths from C₃ to C₁₈, which can be esterified with alcohols of chain length from C₂ to C₁₄ ("Lorol B"). Lippincott presents pour point data in its examples, but the measurements given are for a copolymer-test oil mixture, not the pure copolymer itself.

U.S. Pat. No. 3,314,908 to Kagan et al. teaches the use of C₄ to C₉ olefin in the copolymer and is concerned with the preparation of tough, flexible solids suitable as paint vehicles.

Japanese Publication 157687/1980 (Mitsubishi) discloses copolymers of C₄ to C₁₈ α-olefins and α-β-unsaturated dicarboxylic acid esterified with C₁ to C₁₈ alcohols. Mitsubishi shows a pour point as low as -18° C. with a C₈ alcohol esterifying agent and α-olefin chain length of C₁₆ -C₁₈. Higher pour points are shown or implied for combinations of other olefins and esterifying alcohols.

U.S. Pat. No. 2,543,964 (Glammaria) discloses copolymers of olefins up to C₃₀ chain length and polybasic acids esterified with alcohols having "as few as twelve or perhaps even fewer carbon atoms" but data is not given for any alcohol lighter than C₁₂.

The above described prior art illustrates that lubricating oils have been sought for a long time which display a low pour point without additives, and which have a smallest possible viscosity variation over a broadest possible temperature range. However, the prior art does not provide knowledge of a family of particular α-olefins and esterifying alcohols having specific ranges of carbon chain lengths which when used in combination consistently provide desirable low pour points.

SUMMARY OF THE INVENTION

Thus, a primary objective of the present invention is to identify a family of α-olefins and alcohols used to esterify an α-β-ethylenically unsaturated dicarboxylic acid which provide the desirable low pour points when the α-olefins and esterified dicarboxylic acid are copolymerized.

Accordingly, in one embodiment the present invention is a lubricant or lubricant additive comprising a liquid copolymer of (a) at least one α-olefin, and (b) at least one α-β-ethylenically unsaturated dicarboxylic acid diester having an alcohol esterifying component in a molar ratio (a):(b) of (i) from 0.5 to 4, the α-olefin being within the range of from C₁₀ α-olefins to C₁₆ α-olefins, C₁₆ α-olefins, if employed, being employed only in mixture with C₁₀ to C₁₄ α-olefin, and the esterifying component of the α-β-ethylenically unsaturated diester being within the range of from C₃ alcohol to C₁₀ alcohol, or (ii) in a molar ratio (a):(b) of less than 2.0 with a C₁₆ α-olefin and C₄ -C₁₀ alcohol esterifying component.

DETAILED DESCRIPTION OF THE INVENTION

The preferred α-β-unsaturated dicarboxylic acid esters employed in the invention are the esters of maleic acid, fumaric acid, citraconic acid, mesaconic acid or itaconic acid. However, the esters of maleic acid and fumaric acid are most preferred.

The mole ratio α-olefin to α-β-unsaturated dicarboxylic acid esters amount preferably to between 0.5 and 4, except as otherwise discussed hereinbelow and except when a C₁₆ α-olefin is employed in which case such ratio is less than 2.0. The esterifying alcohols may be straight chain and/or branched chain.

It was completely unexpected that the copolymers of the present invention are liquids having highly desirable pour point and viscosity characteristics, and that they more substantially improve the pour point and viscosity characteristics of mineral oils and lubricants than the known high-molecular copolymers of very long-chain α-olefins and α-β-unsaturated dicarboxylic acid esters. For example, if the data of Mitsubishi is extrapolated from the above mentioned pour point value of -18° C. where an α-olefin chain length of C₁₆ -C₁₈ is employed to an α-olefin chain length of C₁₀ (still using a C₈ alcohol esterifying agent) the indication is the pour point associated with the C₁₀ α-olefin would be higher than 0° C. As will be shown in the following examples, however, the lower chain length α-olefins in most cases yield substantially lower pour points to that shown in Mitsubishi.

Preferably, α-β-unsaturated dicarboxylic acid diesters are employed, and in particular, maleic acid diester and/or fumaric acid diester.

Particularly good flow and viscosity characteristics of the copolymers are then obtained, when 0.005 mole/mole monomer to 0.05 mole/mole monomer of peroxide catalyst is added. Preferably, the peroxide catalyst is added portionwise at time intervals. According to a refinement of the invention, the addition of the peroxide catalyst follows in such manner that initially the copolymerization is started through addition of a third of the amount of peroxide catalyst, and the residual amount of peroxide catalyst is added in 8-12 portions. α-β-unsaturated dicarboxylic acid dioctylester and α-β-unsaturated dicarboxylic acid dibutylester are particularly preferred α-β-unsaturated dicarboxylic acid esters. The reaction temperature may be between 140° to 210° C. and preferably between 160° and 200° C. Polymerization should be carried out in an inert atmosphere.

In order to arrive at mole ratios of α-olefin to α-β-unsaturated dicarboxylic acid ester from 0.5 to 4 in the polymers, the monomers are used in the mole ratio 0.5 to 7.

The copolymers according to the present invention are in themselves useful on the basis of their viscosity behavior, their lubricity and their low pour points as lubricating oils. They can also be used as additives for the adjustment of viscosity behavior and for lowering of the pour point of mineral oils and lubricants.

The copolymers of the present invention are also useful as lubricants for the shaping treatment of thermoplastics.

The liquid state at room temperature of the copolymers of the present invention allows for a very good miscibility with other processing adjuvants. In particular, the copolymers of the present invention can be used to produce stabilizer-lubricant mixtures for the working up of PVC.

In aqueous emulsions the copolymers according to the present invention can serve as a cooling agent for the cutting, machining and other deformations of metal parts.

The novel features which are considered characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following examples.

EXAMPLE 1

One mole of di-n-octylmaleate and one mole of C₁₂ α-olefin were placed in a suitable reaction vessel. The mixture was heated to 160° C. and 10 portions of 0.005 mole di-tert-butylperoxide each were added in intervals of about 30 minutes. Thirty minutes after the last peroxide addition a vacuum was established and the nonpolymerized olefin was distilled off. The last of the residual olefin was removed in a thin-layer evaporator.

The ratio of olefin to ester in the copolymer was determined from the oxygen content by elementary analysis.

The viscosity was measured with an Ubbelohde viscosity meter.

The molecular weight was determined by means of gel permeation chromatography.

Determination of the pour point was done according to the specification DIN pr En 6.

Determination of the viscosity index followed according to method B of ISO-Norm 2909.

The term "monomer ratio" should be understood to be the mole ratio of employed α-olefin to employed α-β-unsaturated dicarboxylic acid ester.

The term "polymer ratio" refers to the ratio of α-olefin to α-β-unsaturated dicarboxylic acid ester in the copolymerizate.

The copolymerizate obtained in the example had a pour point of -39° C. a molecular weight of 2,500 and a viscosity index of 168.

EXAMPLE 2

In a suitable reaction vessel rinsed with nitrogen, 6 moles C₁₀ -α-olefin and 2 moles dibutylmaleate were added and held under nitrogen atmosphere. The mixture was heated to 200° C., t-butylhydroperoxide was used as a catalyst, and initially 0.03 mole t-butylhydroperoxide and later 10 0.004 mole portions were added. After the end of polymerization, excess olefin and dibutylmaleate were distilled off in a vacuum at 0.01 mm Hg.

The results with other olefins as well as with the mole ratio 1:1 olefin to dibutylmaleate are summarized in the following Table.

                  TABLE 1                                                          ______________________________________                                                       Monomer   Polymer          Pour                                  Test  Olefin  Ratio     Ratio  MW   VI   Point 0° C.                    ______________________________________                                         1A    C.sub.10                                                                               3:1       1.35   1500 121  -29                                   1B    C.sub.12                                                                               3:1       1.85   1320 139  -42                                   1C    C.sub.14                                                                               3:1       1.90   1400 146  -20                                   1D    C.sub.16                                                                               3:1       1.91   1600 152   -9                                   1E    C.sub.10                                                                               1:1       0.96   1350 127  -31                                   1F    C.sub.12                                                                               1:1       0.92   1320 127  -42                                   1G    C.sub.14                                                                               1:1       0.83   1280 133  -32                                   1H    C.sub.16                                                                               1:1       0.94   1370 132  -18                                   ______________________________________                                    

EXAMPLE 3

Maleic acid esters esterified with various C₄ -C₈ alcohols were copolymerized with C₁₀ -α-olefin and C₁₄ -α-olefin in mole ratios 1:1 and 1:3 under otherwise similar conditions. The results are summarized in Table 2. As a comparison, dimethylmaleate was copolymerized with C₁₀ -α-olefin under the same conditions in ratios 1:1 and 1:3. The results show that the latter copolymers that were produced had unacceptably high pour points and with C₁₄ -α-olefin in the ratio 1:1, one obtains a pour point of -4° C. but a viscosity index of only 69.

                                      TABLE 2                                      __________________________________________________________________________             C-Atoms                                                                   C-Atoms                                                                             in the                                                                 Test                                                                              in the                                                                              Ester-                                                                              Monomer                                                                              Polymer       Pour                                          No.                                                                               Olefin                                                                              alcohols                                                                            Ratio Ratio                                                                               MW VI    Point 0° C.                            __________________________________________________________________________     2A 10   4    3     1.35 1500                                                                              121   -29                                           2B 10   6    3     1.10 1650                                                                              152   -48                                           2C 10   8    3     0.93 2300                                                                              149   -35                                           2D 10   4    1     0.96 1350                                                                              127   -31                                           2E 10   6    1     0.85 1580                                                                              150   -32                                           2F 10   8    1     0.63 2000                                                                              133   -35                                           2G 14   4    3     1.90 1400                                                                              146   -20                                           2H 14   6    3     1.58 1400                                                                              147   -33                                           2I 14   8    3     1.86 1750                                                                              144   -31                                           2K 14   4    1     0.38 1280                                                                              133   -32                                           2L 14   6    1     0.77 1520                                                                              135   -24                                           2M 14   8    1     0.88 1880                                                                              134   -20                                           2VI                                                                               10   1    3     0.79 1500                                                                               72    +7                                           2V2                                                                               10   1    1     0.69 2800                                                                              -- solid                                                                             --                                            2V3                                                                               14   1    1     0.54 1300                                                                               69    -4                                           __________________________________________________________________________

EXAMPLE 4

Corresponding to the manner of operation given in Example 1, octylfumarate and octylmaleate, as well as hexylfumarate and hexylmaleate were copolymerized with C₁₀ - and C₁₂ -α-olefins. The results are summarized in Table 3.

                                      TABLE 3                                      __________________________________________________________________________        C-Atoms                                                                     Test                                                                              in the       Monomer                                                                              Polymer    Pour                                          No.                                                                               α-Olefin                                                                      Ester   Ratio Ratio                                                                               MW VI Point 0° C.                            __________________________________________________________________________     3A 10   Octyl-Fumarat                                                                          1     0.89 3250                                                                              173                                                                               -35                                           3B 10   Octyl-Maleat                                                                           1     0.93 2300                                                                              149                                                                               -35                                           3C 12   Octyl-Fumarat                                                                          1     0.69 2350                                                                              161                                                                               -33                                           3D 12   Octyl-Maleat                                                                           1     0.63 2000                                                                              133                                                                               -35                                           3E 10   Octyl-Fumarat                                                                          3     1.38 3000                                                                              169                                                                               -26                                           3F 10   Octyl-Maleat                                                                           3     1.10 1650                                                                              152                                                                               -48                                           3G 12   Octyl-Fumarat                                                                          3     1.73 2300                                                                              157                                                                               -33                                           3H 12   Octyl-Maleat                                                                           3     1.84 1500                                                                              146                                                                               -38                                           __________________________________________________________________________

EXAMPLE 5

Thirty-six mole C₁₄ -C₁₆ -α-olefin were mixed in a reactor with 2-ethylhexylmaleate, rinsed with nitrogen and heated to 0° C. At intervals of 30 minutes, 11 portions, each 0.08 mole di-t-butylperoxide were added. Thirty minutes after the last peroxide addition, the volatile products were distilled off with increasing vacuum. Further copolymers were produced according to this method, and are summarized with their measured data in Table 4.

                  TABLE 4                                                          ______________________________________                                         Test             Monomer   Polymer     Pour                                    No.  Ester       Ratio     Ratio  MW   Point 0° C.                      ______________________________________                                         4A   2-ethylhexyl-                                                                              1         0.6    1500 -39                                          maleate                                                                   4B   2-ethylhexyl-                                                                              3         1.4    1450 -30                                          maleate                                                                   4C   dibutylmaleate                                                                             1         0.78   1600 -29                                     4D   2-ethylhexyl-                                                                  fumarate    1         0.7    1700 -29                                     4E   dibutylfumarate                                                                            1         0.7    1700 -23                                     ______________________________________                                    

EXAMPLE 6

To ascertain as precise as practical the parameters of the present invention a further series of copolymers was prepared with unbranched α-olefins (except for small amounts of branched and internal olefins which are usually present in commercially available α-olefins) ranging from C₈ to C₁₆₋₁₈ and esterifying alcohols of from C₂ to C₁₂. The higher chain length alcohols tested were both branched and unbranched and there was no discernable difference in resulting pour point with each type, except where two numbers separated by a (/) are shown, in which case the first number is associated with branched and the second with unbranched.

Each olefin and maleate (esterified maleic acid anhydride) combination (molar ratio 1/1, 2/1 or 3/1) were placed in a suitable reaction vessel under nitrogen atmosphere. At the reaction temperature (in case of C₈ olefin 120° C.; otherwise 160° C.) di-tert-butylperoxide (0.05 mol per mol olefin intake) was added in 10 portions within 3 hours. After additional 30 minute stirring at the reaction temperature all unreacted materials were removed in vacuo.

The pour point of each copolymer prepared was measured and the results are summarized in Table 5.

Table 5 shows a very well defined grouping of copolymers having highly desirable pour points of about -20° C. and lower. Beginning with C₁₀ olefins (C₈ olefins are not included because they are not viable due to their low boiling points), we find the upper limit to be mixtures of C₁₄₋₁₆ olefins (containing not greater than about 30-35 mole % C₁₆ olefin) with esterifying alcohols of C₃ -C₁₀. When the α-olefin:diester ratio is less than 2.0 higher concentrations of C₁₆ α-olefin up to essentially pure C₁₆ -α-olefin may be used in combination with a C₄ -C₁₀ alcohol esterifying component.

The above examples describe and illustrate a well defined family of copolymers not hinted at by the prior art. All copolymers within this family possess acceptably low pour points which are in the overwhelming majority of cases lower than pour points achieved by any prior art copolymers.

                                      TABLE 5                                      __________________________________________________________________________     Pour Points °C.                                                         Alcohol                                                                              Olefin                                                                              C.sub.8                                                                              C.sub.10                                                                          C.sub.12                                                                          C.sub.14                                                                          C.sub.14-16                                                                        C.sub.16                                                                          C.sub.16-18                                   __________________________________________________________________________     C.sub.12                                                                             (1/1)      -15      -3                                                         (2/1)                                                                          (3/1)      -21      -3                                                   C.sub.10                                                                             (1/1)                                                                               -38   -40                                                                               -35                                                                               -26                                                                               -25 -18                                                    (2/1)                                                                          (3/1)                                                                               -39   -40                                                                               -30                                                                               -19                                                                               -17                                                  C.sub.9                                                                              (1/1)      -30      -35                                                        (2/1)                                                                          (3/1)      -38      -28                                                  C.sub.8                                                                              (1/1)                                                                               -23/-37                                                                              -35                                                                               -33                                                                               -20                                                                               -39 -22                                                                               -17                                                 (2/1)                   -10                                                    (3/1)                                                                               -24/-36                                                                              -35                                                                               -33                                                                               -20                                                                               -33 -7                                               C.sub.6                                                                              (1/1)                                                                               -34   -32   -24    -20                                                    (2/1)                                                                          (3/1)      -48   - 33                                                    C.sub.4                                                                              (1/1)                                                                               -14   -31                                                                               -42                                                                               -32                                                                               -29 -18                                                                               -7                                                  (2/1)                                                                          (3/1)                                                                               -19   -29                                                                               -42                                                                               -20                                                                               -27 -9                                               C.sub.3                                                                              (1/1)                                                                               -3    -20      -27 -14                                                    (2/1)      -32                                                                 (3/1)                                                                               -8    -35      -25 -3                                               C.sub.2                                                                              (1/1)      -9       -18    -1                                                  (2/1)                                                                          (3/1)                                                                    __________________________________________________________________________

While the invention has been illustrated and described as embodied in copolymers from α-β-unsaturated dicarboxylic acid esters, methods for their production as well as their use, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims. 

We claim:
 1. A lubricant additive comprising a liquid copolymer of (a) at least one α-olefin, and (b) at least one α-β-ethylenically unsaturated dicarboxylic acid diester having an alcohol esterifying component in a molar ratio (a):(b) of from 0.5 to 4, the α-olefin being within the range of from C₁₀ α-olefins to C₁₆ α-olefins, C₁₆ α-olefins, if employed, being employed only in mixture with C₁₀ to C₁₄ α-olefin, and the alcohol esterifying component of the α-β-ethylenically unsaturated diester being within the range of from C₃ alcohol to C₉ alcohol, said liquid copolymer having a pour point of about -20° C. or lower and a molecular weight of up to about
 3250. 2. The lubricant or lubricant additive of claim 1 wherein said α-β-unsaturated dicarboxylic acid diester is maleic acid ester or fumaric acid ester.
 3. The lubricant or lubricant additive of claim 1 wherein said α-olefin is unbranched.
 4. The lubricant or lubricant additive of claim 1 wherein said esterifying component is butanol.
 5. A method for lubrication comprising applying the liquid copolymer of claim 1 to items to be lubricated.
 6. A method of lubrication comprising adding the liquid copolymer of claim 1 to a lubricant composition and applying the lubricant composition to items to be lubricated. 